This invention relates to a shock absorber adapted to be used for stopping a movable section of various equipments or stopping an article being transferred, and more particularly to a shock absorber used even in case of emergency such as reckless driving of a movable article or the like.
A shock absorber which has been conventionally used for such a purpose as described above, as shown in FIG. 1, is generally constructed so as to utilize resistance of sealed liquid. More particularly, a conventional shock absorber generally designated by reference numeral 100 in FIG. 1 includes an accumulator 102 arranged in a liquid chamber 104 or a chamber 106 communicating with the liquid chamber 104 in order to absorb liquid of a volume corresponding to volumes of an actuation rod 108 and a piston 110 moving or advancing into the liquid chamber 104. The accumulator 102 is generally formed of a soft rubber material of a single foam.
Unfortunately, the accumulator 102 has a disadvantage that because it is made of a rubber material as described above, closed-cell chambers of the rubber material are broken due to expansion of air when a temperature at which the accumulator 102 is used or stored is increased to a level of 100.degree. C. or more. In addition, the temperature is lowered to a level of 0.degree. C. or below, interstructures or partitions defining the closed-cell chambers are hardened to lead to embrittlement; so that when the accumulator 102 is exposed to a high pressure, it is apt to be broken, to thereby fail to satisfactorily exhibit its function. Thus, the conventional shock absorber has a limitation in serviceability. For example, the conventional shock absorber cannot be used when the service temperature of the shock absorber is caused to be elevated to an excessively high level due to any abnormality or emergency such as reckless driving of a control equipment to which the shock absorber is applied or lowered to an abnormally low level due to any cause.
However, the frequency of such emergency as described above is very low, therefore, a consumer desires a decrease in manufacturing cost of a shock absorber due to disregard for an approach to the above-described problem rather than an increase in the cost due to consideration of the problem. Nevertheless, the conventional shock absorber fails to decrease the manufacturing cost, because the shock absorber 100 requires, in addition to the above-described arrangement of the accumulator 102, arrangement of a return spring 112 for returning the actuation rod 108, as well as a lid member 114 for arranging the return spring 112 at the absorber 100, resulting in the number of parts of the shock absorber being highly increased, leading to an increase in manufacturing cost of the absorber.